Reference Selection Guidelines

The quality of a reference interval verification depends heavily on the selection of appropriate reference individuals. CLSI EP28 requires that the laboratory define and document the criteria used to classify individuals as "healthy." Common exclusion criteria include:

• Current or recent illness, hospitalization, or surgery
• Prescription medications, over-the-counter drugs, or oral contraceptives
• Pregnancy or lactation
• Tobacco use, alcohol consumption, or drug abuse
• Abnormal blood pressure, obesity
• Recent transfusion or blood donation
• Known genetic factors relevant to the analyte

Reference individual samples should mirror the original study's preexamination conditions as closely as possible — including specimen type, collection method, and handling procedures. Geographic and demographic comparability between the original study population and the laboratory's patient population must be considered.